Radio Receiver & Direction Finder AD5872

The Marconi AD57 Transmitter and AD5872 Receiver constituted a comprehensive, paired high-frequency (HF) and medium-frequency (MF) communications suite. This system was vital for large Imperial Airways aircraft, such as the Armstrong-Whitworth Ensign, and was also utilized in maritime applications. It provided essential capabilities for navigation and safety on both European and Empire air routes:

The Marconi AD5872 receiver uses six indirectly heated valves with 12-volt filaments in a high-efficiency superheterodyne circuit optimized for aircraft use.

Valve Lineup

• Two Marconi X.31 triode-hexode frequency changers: One for medium waves (600-2,000 meters) and one for short waves (15-75 meters); each handles HF amplification, first detection, oscillation, and mixing to avoid high-frequency switching.
• One Marconi W.30 variable mu HF pentode: Serves as the intermediate frequency (IF) amplifier at 466 kHz.
• One Marconi WD.30 double diode HF pentode: Functions as a second IF amplifier, second detector, and first-stage LF amplifier.
• Two Marconi H.30 triode valves: One as the second audio frequency amplifier; the other as a separate IF heterodyne oscillator for CW reception.

Operational Notes
Four valves operate during telephony or ICW reception, with the fifth (CW heterodyne) added for CW signals. Dual illuminated tuning dials provide direct wavelength calibration, and medium-wave DF/homing uses a rotatable screened frame aerial with a reversing switch (visual indicator optional).

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